1. Field of Invention
This invention relates to computer software for quality control applications of semiconductor production lines, particularly, a software package for extending namespace classifications in the analysis of production data.
2. Description of the Prior Art
Software packages are increasingly being written for Windows.RTM. formats so that a user may interact with the program through symbols on the computer screen via mouse clicks or arrow keys. Such programs are typically written in Visual C++ or Visual Basic programming language, and permit the programmer to call on generalized programming objects to display selectable data input fields. These programs are more user-friendly and afford greater flexibility because the user can choose to select from any one of a large number of program functions based upon displayed visual cues.
Object oriented programming permits a programmer to call upon a particular functional subroutine in Windows.RTM. which is modular in design and operable across a large number of different hardware systems. One primary advantage of Windows.RTM. is that a great number of programming objects are included in the basic system. Examples of visual objects are the classes of buttons, list boxes, dialog boxes, toolbars, scroll bars, menu bars and title bars. Mouse functions are also enabled. A programmer working within a Windows.RTM. environment has access to all of these objects, adding considerable power to his programming abilities.
Quality control has historically relied upon automated computer systems. The automated production line replaces the manual laborer and automated quality control eliminates the inspectors. One important consumer of quality control is the semiconductor industry. Microscopic defects in a semiconductor wafer have major implications on the cost and yield of a semiconductor production process. Because semiconductor technology is so sensitive to defects, isolating their precise source in the production process facilitates great advancement in the industry.
Quality control software packages are currently available for the semiconductor industry, but the programs are generally written on a project-specific basis. These programs are written to include a large number of analytical utilities around a core system but these utilities are essentially fixed in number and the program is difficult to modify. Thus, these packages are expensive and lacking in flexibility.
One method of measuring the number and location of defects in a semiconductor chip involves filtering or erasing the non-defect data from the production data to leave only the defect data. A map of actual production data either may be compared to a map of another set of actual production data, or to a map of an ideal set of production data stored in the computer memory. The defect data is then analyzed according to number, density, location, type and step in the production process, with the goal of correcting the production process itself. The defect data may give clues about how to increase the yield and decrease the cost of the product.
A variety of prior art data analysis systems and methods have been disclosed for industrial process control of semiconductor manufacturing. Among these is U.S. Pat. No. 5,226,118 to Baker et al. This patent discloses a system for making charts. The charts are displayed as a gallery of cells where each cell is a unit of a two dimensional array. Each cell in the chart may be defined as a mathematical function of one or more other cells in a manner similar to a spreadsheet program such as Microsoft Excel..RTM.
Other related patents are U.S. Pat. Nos. 4,967,381; 4,951,190; 4,873,623; 4843,538; 4,805,089; and 4,679,137. These patents disclose a complex multilevel set of data structures. While the control parameters can be changed to some extent by the engineer, the set of parameters is predefined by the software package. Moreover, not all parameters can be changed, and the extent to which a given operator may change them depends upon the operator's level of authorization. These systems are somewhat primitive because they do not recognize the flexibility afforded by object-oriented visual programming.